What CSM is and why you might disable it

CSM stands for Compatibility Support Module. It is a BIOS feature that lets your computer run older software and hardware designed for an outdated system called UEFI's predecessor, called Legacy BIOS. When CSM is on, your motherboard translates commands from old programs so they work on modern hardware.

You disable CSM when you want to use only modern, faster boot methods — or when you are installing a fresh operating system that works better without it. Turning off CSM also closes a potential security gap, since Legacy mode is no longer actively maintained by most manufacturers. If your computer runs fine and you have no reason to use old software, disabling CSM will not hurt anything.

The trade-off is simple: with CSM off, very old external drives, installation media, or hardware will not work. Most people never notice because they do not use anything that old. If you do use legacy equipment, leave CSM on.

Key Takeaways

  • CSM lets your computer run older software and hardware, but it slows down boot time slightly and creates a small security risk.
  • You turn off CSM in the BIOS setup menu by finding the Compatibility Support Module or Legacy Boot option and changing it from Enabled to Disabled.
  • After you disable CSM, your computer will only boot from modern UEFI drives, so old USB drives or installation discs may stop working.
  • If you are installing Windows 11 or a recent Linux distribution, disabling CSM beforehand makes the installation cleaner and faster.
  • You can turn CSM back on at any time by returning to the BIOS menu, so there is no permanent risk to experimenting.

How to enter your BIOS and find the CSM setting

To disable CSM, you first need to open your BIOS setup menu. Restart your computer and watch the screen during startup. Most computers show a message like "Press Delete to enter Setup" or "Press F2 to enter BIOS" — the key varies by manufacturer. Common keys are Delete, F2, F10, or F12. Press the key repeatedly as soon as you see the message, before Windows or your operating system loads.

Once you are in the BIOS menu, look for a section called Boot, Advanced, or Security. The CSM setting might be labeled "Compatibility Support Module," "Legacy Boot," "Legacy Support," or "CSM Support." Different manufacturers use different names. If you cannot find it in the first section you check, move through the menu tabs at the top of the screen until you locate it.

If your computer is very new or uses a modern BIOS interface with a graphical menu (rather than text), CSM may already be disabled by default, and you might not see the option at all. This is normal — manufacturers are phasing out Legacy mode support.

The steps to disable CSM

Once you find the CSM setting, the process is straightforward. Highlight the option using your arrow keys and press Enter. A submenu will appear with options like "Enabled" and "Disabled." Select "Disabled" and press Enter to confirm.

After you change the setting, look for a button or menu option to save and exit — usually labeled "Save and Exit" or "Exit and Save Changes." Press Enter on that option. Your computer will restart and the change will take effect immediately.

If you make a mistake or want to undo the change, simply restart, enter the BIOS again, and switch CSM back to Enabled. There is no harm in turning it on and off as you test.

What happens after you disable CSM

Your computer will boot faster — usually by a second or two — because it no longer has to load the Legacy compatibility layer. You will not see any other obvious change during normal use. Programs and files work exactly the same way.

The main difference appears if you try to boot from an old USB drive or installation disc. Your computer will not recognize it as bootable. If this happens, you have two options: turn CSM back on in the BIOS, or create a new bootable drive using a modern tool like Rufus or the Windows Media Creation Tool, which will format it in UEFI mode instead of Legacy mode.

When to disable CSM before installing an operating system

If you are installing Windows 11, Windows 10, or a recent version of Linux, disable CSM before you start the installation. This ensures the installer runs in pure UEFI mode and sets up your system cleanly. The installation will be faster and you will avoid potential conflicts between Legacy and UEFI boot methods.

If you are installing an older operating system — Windows 7, Windows XP, or a Linux distribution from more than five years ago — leave CSM enabled. These systems were designed for Legacy BIOS and may not install or boot properly in pure UEFI mode.

Resetting CSM to its default state

If you disable CSM and later realize you need it, the fix is simple. Restart your computer, enter the BIOS menu the same way you did before, find the CSM setting, and change it back to Enabled. Save and exit. Your computer will restart and CSM will be active again.

Some BIOS menus also have a "Load Defaults" or "Reset to Factory Settings" option. Using this will turn CSM back on along with other original settings, but it will also reset any other changes you made to the BIOS, such as boot order or overclocking settings. Use this option only if you want to reset everything.

Frequently Asked Questions

Will disabling CSM break my computer?

No. Disabling CSM only affects how your computer boots and runs very old software. Modern programs, files, and hardware work the same way. If something does break, you can turn CSM back on in the BIOS within minutes.

Does disabling CSM make my computer more secure?

Slightly. Legacy BIOS mode is no longer updated by manufacturers, so it has known security gaps that UEFI does not. Disabling CSM closes access to those gaps. However, this is a small benefit — your firewall and operating system updates matter much more for security.

Can I disable CSM if I use old printers or external drives?

If those devices boot from USB or need to run their own firmware, leave CSM on. If they just connect and work like normal peripherals, disabling CSM will not affect them. Test by disabling CSM and seeing if the devices still work — you can always turn it back on.

What if I cannot find CSM in my BIOS menu?

Your computer may already have CSM disabled by default, or the manufacturer may not offer the option. Check your motherboard manual or the manufacturer's website to confirm. You can also look for similar options like "Legacy Support," "UEFI Boot," or "Secure Boot" — these settings are often related.

Do I need to disable CSM to install Windows 11?

No, but it is recommended. Windows 11 can install with CSM on, but disabling it first ensures a cleaner installation and avoids potential boot conflicts. If you forget to disable it beforehand, you can do so after installation and Windows will still work.